Mrthfx

Can a Cauchy sequence converge for one metric while not converging for another?

Is it unprofessional to ask if a job posting on GlassDoor is real?

How can I prevent hyper evolved versions of regular creatures from wiping out their cousins?

NMaximize is not converging to a solution

Malformed Address '10.10.21.08/24', must be X.X.X.X/NN or

Why is Minecraft giving an OpenGL error?

Replacing matching entries in one column of a file by another column from a different file

Can you really stack all of this on an Opportunity Attack?

Why doesn't H₄O²⁺ exist?

Why "Having chlorophyll without photosynthesis is actually very dangerous" and "like living with a bomb"?

Convert two switches to a dual stack, and add outlet - possible here?

RSA: Danger of using p to create q

LaTeX: Why are digits allowed in environments, but forbidden in commands?

How to determine what difficulty is right for the game?

Important Resources for Dark Age Civilizations?

Do I have a twin with permutated remainders?

Does an object always see its latest internal state irrespective of thread?

How to format long polynomial?

Approximately how much travel time was saved by the opening of the Suez Canal in 1869?

Today is the Center

Can a vampire attack twice with their claws using Multiattack?

What typically incentivizes a professor to change jobs to a lower ranking university?

Why are electrically insulating heatsinks so rare? Is it just cost?

What are these boxed doors outside store fronts in New York?

Why doesn't Newton's third law mean a person bounces back to where they started when they hit the ground?

With Newton's third law, why are things capable of moving?Clarification regarding Newton's Third Law of Motion and why movement is possibleAccording to Newton's third law, why don't Action and Reaction make equilibrium?Person Pushing a Block vs. People Pushing off Each Other - Newton's Third LawNewton's third law of motion when moving between two surfacesConfused about Newton's 3rd lawHow did tension developed in a string when two equal and opposite forces are applied on the same body?Why does a Ball bounce back if Forces are Equal and Opposite?Why doesn't an object that collides with one that is at rest just do a 180?Newton's $3^{rd}$ Law of motionWhy does Newton's Third Law work for fields?

10

$begingroup$

Why doesn't a person bounce back after falling down like a ball? If we push a person and he falls down then why doesn't he come back to its initial position. Although according to Newton's 3rd law of motion: To every action there is always equal but opposite reaction. If we take the example of ball then it comes back with the same force as it falls down.But in the case of a human body, this law is not applicable. Why?

newtonian-mechanics forces conservation-laws collision free-body-diagram

share|cite|improve this question

edited 47 mins ago

Aaron Stevens

14.4k42453

asked 12 hours ago

nameera jabeennameera jabeen

593

New contributor

nameera jabeen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Related: physics.stackexchange.com/q/45653/2451 and links therein.
  $endgroup$
  – Qmechanic♦
  11 hours ago
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  A ball does not come back with exactly the same force: youtube.com/watch?v=xXXF2C-vrQE
  $endgroup$
  – StrongBad
  7 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  The law applies to human bodies. But the law doesn't apply to energy. It applies to force. Force isn't the same thing as energy. It isn't force that's gone missing here. It's energy. Ask where the energy went. We have conservation of energy so it's gotta be here somewhere.
  $endgroup$
  – candied_orange
  7 hours ago
  
  
  

  
  
  
  

add a comment | 

10

$begingroup$

Why doesn't a person bounce back after falling down like a ball? If we push a person and he falls down then why doesn't he come back to its initial position. Although according to Newton's 3rd law of motion: To every action there is always equal but opposite reaction. If we take the example of ball then it comes back with the same force as it falls down.But in the case of a human body, this law is not applicable. Why?

newtonian-mechanics forces conservation-laws collision free-body-diagram

share|cite|improve this question

edited 47 mins ago

Aaron Stevens

14.4k42453

asked 12 hours ago

nameera jabeennameera jabeen

593

New contributor

nameera jabeen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Related: physics.stackexchange.com/q/45653/2451 and links therein.
  $endgroup$
  – Qmechanic♦
  11 hours ago
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  A ball does not come back with exactly the same force: youtube.com/watch?v=xXXF2C-vrQE
  $endgroup$
  – StrongBad
  7 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  The law applies to human bodies. But the law doesn't apply to energy. It applies to force. Force isn't the same thing as energy. It isn't force that's gone missing here. It's energy. Ask where the energy went. We have conservation of energy so it's gotta be here somewhere.
  $endgroup$
  – candied_orange
  7 hours ago
  
  
  

  
  
  
  

add a comment | 

$begingroup$

Why doesn't a person bounce back after falling down like a ball? If we push a person and he falls down then why doesn't he come back to its initial position. Although according to Newton's 3rd law of motion: To every action there is always equal but opposite reaction. If we take the example of ball then it comes back with the same force as it falls down.But in the case of a human body, this law is not applicable. Why?

newtonian-mechanics forces conservation-laws collision free-body-diagram

share|cite|improve this question

edited 47 mins ago

Aaron Stevens

14.4k42453

asked 12 hours ago

nameera jabeennameera jabeen

593

New contributor

nameera jabeen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

$endgroup$

share|cite|improve this question

edited 47 mins ago

Aaron Stevens

14.4k42453

asked 12 hours ago

nameera jabeennameera jabeen

593

New contributor

nameera jabeen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

share|cite|improve this question

edited 47 mins ago

Aaron Stevens

14.4k42453

asked 12 hours ago

nameera jabeennameera jabeen

593

New contributor

nameera jabeen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

edited 47 mins ago

Aaron Stevens

14.4k42453

edited 47 mins ago

Aaron Stevens

14.4k42453

asked 12 hours ago

nameera jabeennameera jabeen

593

New contributor

nameera jabeen is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

asked 12 hours ago

nameera jabeennameera jabeen

593

3 Answers
3

active

oldest

votes

43

$begingroup$

Newton's third law just says when the person is hitting the floor the force the person exerts on the ground is equal to the force the ground exerts on the person. i.e. all forces are interactions.

Newton's third law does not say that all collisions are elastic, which is what you are proposing. When someone hits the floor most of the energy is absorbed by the person through deformation (as well as the floor, depending on what type of floor it is), but there is barely any rebound since people tend to not be very elastic. i.e. the deformation does not involve storing the energy to be released back into kinetic energy. Contrast this with a bouncy ball where much of the energy goes into deforming the ball, but since it is very elastic it is able to spring back and put energy back into motion. However, it is unlikely the collision is still perfectly elastic, as you seem to suggest in your question.

Your misunderstanding likely comes from the imprecise usage of the words "action" and "reaction". In this case, these words refer to just forces, not entire processes. You can get some confusing questions if you don't understand this. For example, why is it that when I open my refrigerator that my refrigerator doesn't also open me?

share|cite|improve this answer

edited 6 hours ago

answered 12 hours ago

Aaron StevensAaron Stevens

14.4k42453

$endgroup$

• 
  
  
  

  
  8
  

  
  
  
  
  
  

  
  $begingroup$
  Well, I can’t speak for you, but when I open my refrigerator my mouth invariably opens in return—I had always thought it was in anticipation of what is to follow, but perhaps the refrigerator had been returning the gesture after all !
  $endgroup$
  – eggyal
  10 hours ago
  

  
  
  
  


• 
  
  
  

  
  8
  

  
  
  
  
  
  

  
  $begingroup$
  And, in fact, we cannot make persons more elastic but we can do it with the floor. In general, we call them trampolins. A person falling in a trampoline is very likely to bounce =)
  $endgroup$
  – jean
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @DavidRicherby I suppose it depends on the type of floor as well, but that is a good point. I'll make an edit.
  $endgroup$
  – Aaron Stevens
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  That's deep. I'm going to tweak it and use it to sound wise. "When you take something out of the refrigerator, the refrigerator takes something out of you."
  $endgroup$
  – Lofty Withers
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  If you're going to call a trampoline a floor, I get to call a pogostick rider a person
  $endgroup$
  – Foon
  4 hours ago
  

  
  
  
  

 | 
show 1 more comment

6

$begingroup$

When you body hits the floor, it does receive an equal and opposite reaction force from the floor. But unlike a ball a body is an complex object. So not all energy is transferred back as kinetic energy. Some energy is used to produce sound, some is used to deform your body... etc. I think you are confusing force with energy. Does every ball bounce back the same amount? Newton's 3rd law talks about force only. More force doesn't always(mostly) equal to more work done.

In your case if all the force was used to change the body's kinetic energy somehow(which is not realistically possible), then it would have bounced back the same amount.

share|cite|improve this answer

answered 12 hours ago

LikhonLikhon

1069

$endgroup$

add a comment | 

0

$begingroup$

If we push a person and he falls down then why doesn't he come back to its initial position. Although according to Newton's 3rd law of motion: To every action there is always equal but opposite reaction.

That's not a correct statement of Newton's third law.

Newton's third law of motion actually says: "If one object exerts a force on another object, then the second object also exerts a force on the first object, which is of the same magnitude but in the opposite direction."

So in this case, what Newton's third law is saying is: "If the floor pushes up on a person with a certain amount of force, then the person pushes down on the floor with the same amount of force." From this, there's no reason to think that the person would bounce back to his initial position.

share|cite|improve this answer

answered 4 hours ago

Tanner SwettTanner Swett

1518

$endgroup$

add a comment | 

Your Answer

StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "151"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});

nameera jabeen is a new contributor. Be nice, and check out our Code of Conduct.

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fphysics.stackexchange.com%2fquestions%2f470714%2fwhy-doesnt-newtons-third-law-mean-a-person-bounces-back-to-where-they-started%23new-answer', 'question_page');
}
);

Post as a guest

Name

Email

Required, but never shown

43

$begingroup$

Newton's third law just says when the person is hitting the floor the force the person exerts on the ground is equal to the force the ground exerts on the person. i.e. all forces are interactions.

Newton's third law does not say that all collisions are elastic, which is what you are proposing. When someone hits the floor most of the energy is absorbed by the person through deformation (as well as the floor, depending on what type of floor it is), but there is barely any rebound since people tend to not be very elastic. i.e. the deformation does not involve storing the energy to be released back into kinetic energy. Contrast this with a bouncy ball where much of the energy goes into deforming the ball, but since it is very elastic it is able to spring back and put energy back into motion. However, it is unlikely the collision is still perfectly elastic, as you seem to suggest in your question.

Your misunderstanding likely comes from the imprecise usage of the words "action" and "reaction". In this case, these words refer to just forces, not entire processes. You can get some confusing questions if you don't understand this. For example, why is it that when I open my refrigerator that my refrigerator doesn't also open me?

share|cite|improve this answer

edited 6 hours ago

answered 12 hours ago

Aaron StevensAaron Stevens

14.4k42453

$endgroup$

• 
  
  
  

  
  8
  

  
  
  
  
  
  

  
  $begingroup$
  Well, I can’t speak for you, but when I open my refrigerator my mouth invariably opens in return—I had always thought it was in anticipation of what is to follow, but perhaps the refrigerator had been returning the gesture after all !
  $endgroup$
  – eggyal
  10 hours ago
  

  
  
  
  


• 
  
  
  

  
  8
  

  
  
  
  
  
  

  
  $begingroup$
  And, in fact, we cannot make persons more elastic but we can do it with the floor. In general, we call them trampolins. A person falling in a trampoline is very likely to bounce =)
  $endgroup$
  – jean
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @DavidRicherby I suppose it depends on the type of floor as well, but that is a good point. I'll make an edit.
  $endgroup$
  – Aaron Stevens
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  That's deep. I'm going to tweak it and use it to sound wise. "When you take something out of the refrigerator, the refrigerator takes something out of you."
  $endgroup$
  – Lofty Withers
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  If you're going to call a trampoline a floor, I get to call a pogostick rider a person
  $endgroup$
  – Foon
  4 hours ago
  

  
  
  
  

 | 
show 1 more comment

43

$begingroup$

Newton's third law just says when the person is hitting the floor the force the person exerts on the ground is equal to the force the ground exerts on the person. i.e. all forces are interactions.

Newton's third law does not say that all collisions are elastic, which is what you are proposing. When someone hits the floor most of the energy is absorbed by the person through deformation (as well as the floor, depending on what type of floor it is), but there is barely any rebound since people tend to not be very elastic. i.e. the deformation does not involve storing the energy to be released back into kinetic energy. Contrast this with a bouncy ball where much of the energy goes into deforming the ball, but since it is very elastic it is able to spring back and put energy back into motion. However, it is unlikely the collision is still perfectly elastic, as you seem to suggest in your question.

Your misunderstanding likely comes from the imprecise usage of the words "action" and "reaction". In this case, these words refer to just forces, not entire processes. You can get some confusing questions if you don't understand this. For example, why is it that when I open my refrigerator that my refrigerator doesn't also open me?

share|cite|improve this answer

edited 6 hours ago

answered 12 hours ago

Aaron StevensAaron Stevens

14.4k42453

$endgroup$

• 
  
  
  

  
  8
  

  
  
  
  
  
  

  
  $begingroup$
  Well, I can’t speak for you, but when I open my refrigerator my mouth invariably opens in return—I had always thought it was in anticipation of what is to follow, but perhaps the refrigerator had been returning the gesture after all !
  $endgroup$
  – eggyal
  10 hours ago
  

  
  
  
  


• 
  
  
  

  
  8
  

  
  
  
  
  
  

  
  $begingroup$
  And, in fact, we cannot make persons more elastic but we can do it with the floor. In general, we call them trampolins. A person falling in a trampoline is very likely to bounce =)
  $endgroup$
  – jean
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @DavidRicherby I suppose it depends on the type of floor as well, but that is a good point. I'll make an edit.
  $endgroup$
  – Aaron Stevens
  6 hours ago
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  $begingroup$
  That's deep. I'm going to tweak it and use it to sound wise. "When you take something out of the refrigerator, the refrigerator takes something out of you."
  $endgroup$
  – Lofty Withers
  4 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  If you're going to call a trampoline a floor, I get to call a pogostick rider a person
  $endgroup$
  – Foon
  4 hours ago
  

  
  
  
  

 | 
show 1 more comment

$begingroup$

Newton's third law just says when the person is hitting the floor the force the person exerts on the ground is equal to the force the ground exerts on the person. i.e. all forces are interactions.

Newton's third law does not say that all collisions are elastic, which is what you are proposing. When someone hits the floor most of the energy is absorbed by the person through deformation (as well as the floor, depending on what type of floor it is), but there is barely any rebound since people tend to not be very elastic. i.e. the deformation does not involve storing the energy to be released back into kinetic energy. Contrast this with a bouncy ball where much of the energy goes into deforming the ball, but since it is very elastic it is able to spring back and put energy back into motion. However, it is unlikely the collision is still perfectly elastic, as you seem to suggest in your question.

Your misunderstanding likely comes from the imprecise usage of the words "action" and "reaction". In this case, these words refer to just forces, not entire processes. You can get some confusing questions if you don't understand this. For example, why is it that when I open my refrigerator that my refrigerator doesn't also open me?

share|cite|improve this answer

edited 6 hours ago

answered 12 hours ago

Aaron StevensAaron Stevens

14.4k42453

$endgroup$

share|cite|improve this answer

edited 6 hours ago

answered 12 hours ago

Aaron StevensAaron Stevens

14.4k42453

answered 12 hours ago

Aaron StevensAaron Stevens

14.4k42453

answered 12 hours ago

Aaron StevensAaron Stevens

14.4k42453

6

$begingroup$

When you body hits the floor, it does receive an equal and opposite reaction force from the floor. But unlike a ball a body is an complex object. So not all energy is transferred back as kinetic energy. Some energy is used to produce sound, some is used to deform your body... etc. I think you are confusing force with energy. Does every ball bounce back the same amount? Newton's 3rd law talks about force only. More force doesn't always(mostly) equal to more work done.

In your case if all the force was used to change the body's kinetic energy somehow(which is not realistically possible), then it would have bounced back the same amount.

share|cite|improve this answer

answered 12 hours ago

LikhonLikhon

1069

$endgroup$

add a comment | 

6

$begingroup$

When you body hits the floor, it does receive an equal and opposite reaction force from the floor. But unlike a ball a body is an complex object. So not all energy is transferred back as kinetic energy. Some energy is used to produce sound, some is used to deform your body... etc. I think you are confusing force with energy. Does every ball bounce back the same amount? Newton's 3rd law talks about force only. More force doesn't always(mostly) equal to more work done.

In your case if all the force was used to change the body's kinetic energy somehow(which is not realistically possible), then it would have bounced back the same amount.

share|cite|improve this answer

answered 12 hours ago

LikhonLikhon

1069

$endgroup$

add a comment | 

$begingroup$

When you body hits the floor, it does receive an equal and opposite reaction force from the floor. But unlike a ball a body is an complex object. So not all energy is transferred back as kinetic energy. Some energy is used to produce sound, some is used to deform your body... etc. I think you are confusing force with energy. Does every ball bounce back the same amount? Newton's 3rd law talks about force only. More force doesn't always(mostly) equal to more work done.

In your case if all the force was used to change the body's kinetic energy somehow(which is not realistically possible), then it would have bounced back the same amount.

share|cite|improve this answer

answered 12 hours ago

LikhonLikhon

1069

$endgroup$

share|cite|improve this answer

answered 12 hours ago

LikhonLikhon

1069

answered 12 hours ago

LikhonLikhon

1069

answered 12 hours ago

LikhonLikhon

1069

0

$begingroup$

If we push a person and he falls down then why doesn't he come back to its initial position. Although according to Newton's 3rd law of motion: To every action there is always equal but opposite reaction.

That's not a correct statement of Newton's third law.

Newton's third law of motion actually says: "If one object exerts a force on another object, then the second object also exerts a force on the first object, which is of the same magnitude but in the opposite direction."

So in this case, what Newton's third law is saying is: "If the floor pushes up on a person with a certain amount of force, then the person pushes down on the floor with the same amount of force." From this, there's no reason to think that the person would bounce back to his initial position.

share|cite|improve this answer

answered 4 hours ago

Tanner SwettTanner Swett

1518

$endgroup$

add a comment | 

0

$begingroup$

If we push a person and he falls down then why doesn't he come back to its initial position. Although according to Newton's 3rd law of motion: To every action there is always equal but opposite reaction.

That's not a correct statement of Newton's third law.

Newton's third law of motion actually says: "If one object exerts a force on another object, then the second object also exerts a force on the first object, which is of the same magnitude but in the opposite direction."

So in this case, what Newton's third law is saying is: "If the floor pushes up on a person with a certain amount of force, then the person pushes down on the floor with the same amount of force." From this, there's no reason to think that the person would bounce back to his initial position.

share|cite|improve this answer

answered 4 hours ago

Tanner SwettTanner Swett

1518

$endgroup$

add a comment | 

$begingroup$

If we push a person and he falls down then why doesn't he come back to its initial position. Although according to Newton's 3rd law of motion: To every action there is always equal but opposite reaction.

That's not a correct statement of Newton's third law.

Newton's third law of motion actually says: "If one object exerts a force on another object, then the second object also exerts a force on the first object, which is of the same magnitude but in the opposite direction."

So in this case, what Newton's third law is saying is: "If the floor pushes up on a person with a certain amount of force, then the person pushes down on the floor with the same amount of force." From this, there's no reason to think that the person would bounce back to his initial position.

share|cite|improve this answer

answered 4 hours ago

Tanner SwettTanner Swett

1518

$endgroup$

share|cite|improve this answer

answered 4 hours ago

Tanner SwettTanner Swett

1518

answered 4 hours ago

Tanner SwettTanner Swett

1518

answered 4 hours ago

Tanner SwettTanner Swett

1518